Optical disc substrates are produced from a material such as aromatic polycarbonate resin, acrylic resin, epoxy resin, or glass. Among them, plastic resins are generally employed, for reasons such as easy formation of fine molded articles through injection molding and adaptability to large-scale production.
Among these resins, polycarbonate resin is preferably employed, in that it satisfies properties required of optical disc substrates such as strength (e.g., impact strength), transparency, heat resistance, and low water absorption.
Meanwhile, if flashes generate around optical disc substrates during injection molding, they may be scratched off from an optical disc substrate when the optical disc substrate is released or ejected from molds. As the result, they may become floating dusts. These dusts may attach to the surface of the released optical disc substrates, or may attach to the mold and be incorporated into another optical disc substrate which is subsequently molded. Such dusts on the optical disc substrates or inside the optical disc substrates are detected as foreign matters or optical, when they are inspected by disc-inspection scanner. Thus, such dusts may sacrifice the yield of optical disc substrates.
On the other hand, to prevent such flashing from generating and to attain smooth mold releasing, the technique to add the mold-releasing agent into an aromatic polycarbonate resin is known.
For example, Japanese Patent Application Laid-Open (kokai) No. Heisei 10(1998)-60105 discloses an aromatic polycarbonate resin for optical disc substrates, containing a C14–C30 fatty acid monoglyceride in an amount of 0.06 to 0.1 mass %.